Air conditioning systems with reheat coils



Aug. 9, 1966 J. R. HARNISH AIR CONDITIONING SYSTEMS WITH REHEAT COILS 2 Sheets-Sheet l Filed May 3. 1965 .PqPmOEmwIP |NVENTOR= JAMES R. HARNISH,

ATTCRNEY Aug.. 9, 1966 J. R. HARNISH AIR CONDITIONING SYSTEMS WITH REHEAT COILS 2 Sheets-Sheei 2 Filed May 3, 1965 |NVENTOR= JAMES RHARNISH,

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' ATTGRNY United States Patent() 3,264,840 AlR CNDETIONING SY'EMS WITH REHEAT COI .lames R. Hamish, Staunton, Va., assignor to Westinghouse Electric Corporation, Pittsburgh, Ia., a corporation of Pennsylvania Filed May 3, 1965, Ser. No. 452,480 8 Claims. (Cl. 62-173) This invention relates to air conditioning systems in which reheat is used for increasing the sensible heat of air which has been chilled, for dehumidication, to a temperature which is too low for comfort, and has las an object to improve such systems.

In many locations, the wet bulb temperature of the outdoor is frequently so high that where the utmost in comfort is desired, it is necessary to chill the lair to be conditioned below its dewpoint temperature, and then to reheat the air to increase its dry bulb temperature. This has been accomplished in many ways, including using the heat in recirculated air in Sio-called by-pass systems, and using the heat from condensers of refrigeration systems.

This invention uses a reheat coil which is connected in series with a condenser coil to operate as an 4auxiliary condenser coil when reheat is required. An expansion valve is used which supplies refrigerant liquid to the associated evaporator coil at the rate at which refrigerant is condensed in the condenser coil when no reheat is required, and at the rate at which refrigerant is condensed in the condenser and reheat coils when reheat is required, so that the condenser and reheat coils are adequately drained for good heat transfer. This results in the evaporator coil being supplied with more refrigerant liquid than it can evaporate. The unevaporated liquid is supplied into a suction line accumulator where it is evaporated by heat from the high pressure liquid supplied to the expansion valve. A valve controlled by a thermostat connects the reheat coil in series with the condenser coil when reheat is required. In a heat pump, the reheat coil is used as an axiliary condenser coil during air heating operation.

This invention will now be described with reference to the annexed drawings, of which:

IFIG. l is a diagrammatic view of an air conditioning system embodying this invention;

FIG. 2 is a sectional view of the expansion valve used in the system of FIG. 1, and

FIG. 3 is a diagrammatic view of a heat pump embodying this invention.

Description of FIG. 1

The discharge side of a hermetic refrigerant compressor C driven by an enclosed electric motor CM, is connected by discharge gas tube 10 to one end of condenser coil 11, the other end of which is connected by tube 12, three-way valve 13, tube 14, heat exchange coil 15 within accumulator 16, tube 17, expansion'valve 18, and tube 19 to one end of air cooling evaporator coil 20. The other end of the coil 20 is connected by tube 21 to the upper portion of the interior of the accumulator 16. U-shaped tube 22 within the accumulator 16 has an open end 23, and its other end is connected by suction gas tube 24 to the suction side of the compressor C. Portions of the tubes 14 and 24 are in heat exchange contact.

A fan 26 driven by an electric motor 27 moves indoor air to be chilled over the coil 20. A fan which is not shown, could be used to move outdoor -air over the condenser coil 11 when the latter is air cooled.

The three-way valve 13 is also connected by tube 30 to one end of reheat coil 31, the other end of which is connected by tube 32, check-valve 33 and tube 34 to the ICC vlines L1 and L2 respectively. The switches S1 and S2 are switches of motor starter MS which has an energizing coil 40 which is connected in series with switch HS of humidistat H to the lines L1 and L2. Switch TS2 of the thermostat T is connected across the switch HS.

The expansion valve 18, lshown in detail by FIG. 2, has a diaphragm chamber 42, the outer portion of which is connected by capillary tube 52 to thermal bulb S3 in heat exchange contact with the tube 14. The inner portion of the diaphragm chamber 42 is connected by capillary tube 54 to the interior of the tube 14. The bulb 53 contains the same refrigerant that is used in the system of FIG. 1.

The system of FIG. l contains a refrigerant charge that is larger than is necessary to satisfy the requirements of the system so that there is always a quantity of refrigerant liquid within the accumulator 16.

Description 0f FIG. 2

The valve 18 is a subcooling control valve such as is disclosed in my Patent No. 3,171,263. Its diaphragm chamber 42 has a diaphragm 43 extending across its center, and which is connected at its center to the upper end of rod 44, the lower end of which is connected to valve piston 45 within valve chamber 46. A coiled spring 47 having its upper end in contact with the bottom wa-ll of the diaphragm chamber 42, and its lower end in contact with the top of the piston 45 extends around the rod 44. The valve chamber 46 has an inlet connected to the tube 17, and an. outlet connected to the tube 19. A partition 50 extends across the chamber 46 between its inlet and outlet, and has a valve opening 51 below the piston 45. The spring 41 biases the piston 45 towards closed position.

Operation of FIGS. 1 and 2 The starter MS is energized by the closing of the humidistat switch TS when the relative humidity of the indoor air increases, for example, above 50%, or by the closing of the thermostat switch TS2 when the indoor temperature increases, for example 'above 80 F., and closes lits switches S1 and S2, starting the compressor mot-or CM. Discharge gas from the compressor C is supplied through the tube 10 into the condenser coil 11. Refrigerant liquid from the coil 11 ows through the tube 12, and if no reheat is required, through the three-way valve 13, the tube 14, the coil 15 within the accumulator 16, the tube 17, the expansion valve 18 and the tube 19 into the evaporator coil 20. The expansion valve 18 -operates to supply to the evaporator coil 20 all of the condensed refrigerant. An increase in the temperature of the liquid within the tube 14 tends to close the valve 18 so as to back up more liquid within the condenser coil 11 for increasing the subcooling of the liquid. Increased liquid pressure within the tube 14- -tends to open the valve 18. For an increase in the r-ate at which refrigerant is condensed, if the valve 18 is not open sufficiently, liquid will back up in the condenser coil until the pressure is increased suiciently or the temperature is reduced sufciently, to cause the valve 18 to open further. When the condensing rate changes, the valve 18 readjusts accordingly as do all modulating expansion valves, and meters refrigerant liquid to the evaporator coil Iat the rate at which the liquid is condensed as does an expansion valve controlled by a high pressure float.

In the system of FIG. 1, the valve 18 m-aintains, for example, F. subcooling of the liquid flowing from the condenser coil, at a condensing temperature of 100 F., and is preferred for this reason. However, `a conventional expansion valve controlled by ya high pressure oat, could be used without the subcooling advantage.

Since the evaporator coil 20 receives more refrigerant liquid than it can evaporate, its interior surface is thoroughly wetted for increased heat transfer. The unevaporated liquid passes with the gas from the evaporated liquid, through the tube 21 into the accumulator 16. Heat from the high pressure liquid flowing through the coil evaporates the excess liquid at the rate at which it is supplied into the accumulator. The liquid flowing through the coil 15 is further subcooled by this action. Gas is separated from the liquid within the accumulator 16, and passes through the tube 24 to the suction side of the compressor C. Any refrigerant liquid entering the tube 24 is evaporated by heat from the liquid owing through the tube 14 with which the tube 24 is in contact, Athe liquid flowing through the tube 14 being further subcooled by this action.

When the humidistat H is in control of the compressor, the indoor air may be chilled to such a low temperature that reheat is required. When this happens, the switch TS1 of the thermostat T closes at, for example, 78 F., and energizes the solenoid S which adjusts the three-way valve 13 to discontinue supplying liquid from the condenser coil 11 directly into the tube 14, and to supply the refrigerant leaving the condenser coil 11, through the tube 30, the reheat `coil 31 operating as an auxiliary condenser coil, the tube 32 and the checkvalve 33 into the tube 14. From this point on, the system operates as described in the foregoing except that heat from the reheat coil 31 raises the dry bulb temperature of the air leaving the evaporator coil to a comfortable temperature.

Since the expansion valve 18 acts to maintain the coils 11 and 31 adequately drained, their etlciency is increased, and the coil 31 elfectively reheats the chilled arr.

Description of FIG. 3

Those components of FIG. 3 which correspond to components of FIG. 1 are given the same reference characters.

Compressor C, driven by enclosed electric motor CM, is connected by discharge gas tube 10 to a conventional four-way reversal valve RV, adjustable by a solenoid RVS and by tube 60 to one end of indoor air coil 61, the other end of which is connected by tube 62, checkvalve 63, tube 64, check-valve 65 and tube 66 to one end of outdoor coil 67. The other end of the coil 67 is connected by tube 68 to the reversal valve RV. The reversal valve RV is also connected by tube 69 to the top of the accumulator 16. U-shaped tube 22 within the accumulator 16 has an open upper end 23, and its other end is connected by suction gas tube 24 to the suction side of the compressor C. The tube 64 is connected by tube 70, expansion valve 18, heat exchange coil 1S within the accumulator 16, tube 14, three-way valve 13 adjustable by solenoid S, tube 72, check-valve 73 and tube 74 to the tube 66. The valve 13 is also connected by tube 75 to one end of reheat coil 31, which end is also connected through tube 76 and check-valve 79 to the tube 62. The other end of the coil 31 is connected by tube 77 and check-valve 78 to the tube 14.

The expansion valve 18 is a subcooling control valve as described in the foregoing, and has a diaphragm chamber 42, the outer portion of which is connected by capillary tube 52 to thermal bulb 53 in heat exchange contact with the tube 14. The inner portion of the diaphragm chamber 42 is connected by capillary tube S4 to the interior of the tube 14. The bulb 53 contains the same refrigerant that is used in the heat pump of FIG. 3.

A fan 26 driven by an electric motor 27, moves indoor air over the coils 61 and 31. A fan which is not shown, could be used to move outdoor air over the coil 67 if the latter is an air contacting coil.

The compressor motor CM is connected by wires 36 and 37, switches S1 and S2 respectively, of motor starter MS to electric supply lines L1 and L2 respectively. Energizing coil 40 of the starter MS is connected at one end to the line L1, and at its other end through switch contacts S3, switch blade B1 normally in contact with the contacts S3, and switch HS of hurnidistatA H to the line L2. Switch TS2 of dry bulb thermostat T is connected across the switch HS. The other end of the coil 40 is also connected through switch contacts S4 normally spaced from the blade B1, and the latter when the latter is moved against the contacts S4, to switch TS3 of the thermostat T, which switch TS3 is connected to the line L2. The solenoid S is connected to the line L1, and through switch contacts S5 normally in contact with switch blade B2, the blade B2 and switch TS1 of the thermostat T to the line L2. The solenoid RVS is connected by wire 80 to the line L1, and by wire 81, switch contacts S6 and switch blade B3 when the latter is moved against the contacts S6, and by wire 82 to the line L2.

The switch blades B1, B2 and B3 are attached to a rod 84 of electric insulation which is movable lengthwise by a knob 85. The rod 84 has an indicator arrow 86 shown opposite Cooling marker 87, and movable with the rod opposite Heating marker 88. FIG. 3 shows the switch blades and their associated switch contacts in positions for air cooling operation of the heat pump.

Air cooling operation of FIG. 3

The starter MS of the compressor motor CM is energized by the closing of the switch HS of the humidistat H when the relative humidity of the indoor air is too high, or by the closing of the switch TS2 of the thermostat T when the dry bulb temperature of the indoor air is too high, and closes its switches S1 and S2, starting the motor CM. Discharge gas from the compressor C ows through the tube 10, the reversal valve RV, and the tube 68 into the outdoor coil 67 operating as a condenser. The valve RV is in its cooling position at this time due to the solenoid RVS being deenergized. Liquid from the coil 67 tlows through the tube 74, the checkvalve 73, and if no reheat is required, through the threeway valve 13, the tube 14, the coil 15, the expansion valve 18, the tubes 70 and 64, the check-valve 63 and the tube 62 into the indoor coil 61 operating as an evaporator. The expansion valve 18 operates as described in the foregoing in connection with FIGS. l and 2. Gas and unevaporated liquid flow from the coil 61 through the tube 60, the reversal valve RV and the tube 69 into the accumulator 16. Gas separated from the liquid within the accumulator lows through the suction lgas tube 24 to the suction side of the compressor C. Heat from the coil 1S evaporates the excess refrigerant liquid flowing into the accumulator at the rate at which it flows into the latter, the liquid flowing through the coil 15 being subcooled by this action. Heat from the liquid flowing through the tube 14 evaporates any liquid refrigerant which may enter the tube 24 through the heat exchange contact between the tubes 14 and 24, the `liquid owing through the tube 14 being cubcooled by this action.

When reheat is required, the switch TS1 of the thermostat T closes, and connects through the switch contacts S5 and the switch blade B2, the solenoid S to the supply lines L1 and L2. The solenoid S is energized and adjusts the three-way valve 13 to prevent the flow of refrigerant from the tube 72 into the tube 14, and to permit refrigerant to ow from the tube 72 into the tube 75 and from the latter through the reheat coil 31, the tube 77 and the check-valve 78 into the tube 14, and from the latter through the coil 15, the expansion valve 18, the tubes 70 and 64, the check-valve 63 and the tube 62 into the indoor coil 61 operating as an evaporator. Expanded refrigerant from the tube 62 cannot flow through the check-valve 79 and the tube 76 into the coil 31 since the tube 75 supplies high pressure refrigerant at the junction of the tubes 75 and 76.

Heat from the condensing refrigerant flowing through the coil 31 increases the sensibe heat in the air dehumied by the coil 61 to that required for comfort. The liquid owing through the coil 31 is also subcooled by this action.

Air heating operation of FIG. 3

To convert to air heating operation, the control knob 85 should be moved to the right of the position shown by FIG. 3, to place its indicator arrow 86 `opposite the Heating marker 88. This would move the switch blade B3 against the switch contacts S6, energizing the solenoid RVS which would adjust the reversal valve RV to its air heating position. This would also move the switch blade B2 from contact with the switch contacts S5, deenergizing the solenoid S of the three-way valve 13. This would also move the switch blade B1 from contact with the switch contacts S3, disconnecting the switch HS of the humidistat H, and the switch TS2 of the thermostat T from control of the motor starter MS, and would move the blade B1 in cont-act with the switch contacts S4, placing the switch TS3 of the thermostat T in control of the motor starter MS.

When the thermostat T calls for heat, its switch TS3 closes at, for example, 73 F. to energize the starter MS which closes its switches S1 and S2, starting the compressor motor CM. Discharge gas from the compressor C liows through the tube 10, the reversal valve RV and the tube 60 into the indoor coil 61 operating as a condenser. Refrigerant from the coil 61 flows through the tube 62, the check-valve 79 and the tube 76 into the reheat coil 31 operating as an auxiliary condenser. Liquid from the coil 31 flows through the tube 77, the checkvalve 78, the tube 14, the coil 15, the expansi-on valve 18, the tube 70, the check-valve 65 and the tube 66 into the outdoor c-oil 67 operating as an evaporator. Gas and unevaporated liquid flowing from the coil 67 flow through the tube 68, the reversal valve RV and the tube 69 linto the accumulator 16. Gas separated from the liquid within the accumulator flows through the suction gas tube 24 to the suction side of the compressor C.

During air cooling and air heating operation of the heat pump of FIG. 3, the expansion valve 18 operates to control subcooling yof the condensed refrigerant, and to supply to the coil operating as an evaporator, refrigerant liquid at the rate at which it is condensed. The coil operating as an evaporator is supplied with more refrigerant liquid than it can evaporate, with the excess liquid flowing into the accumulator 16 where it is evaporated by heat from the coil at the rate at which it is supplied into the accumulator as described in connection with FIG. l, the liquid flowing through the coil 15 being subcooled by this action. The refrigerant which is condensed is that evaporated within the coil 61 or 67 plus that evaporated within the accumulator 16. Any refrigerant liquid entering the suction gas tube 24 is evaporated by heat from the tube 14 with which it is in contact, the liquid owing through the tube 14 being subcooled by this action.

The coil 67 may be in heat exchange with air, or may be part of a shell-and-tube heat exchanger through which water or another liquid is circulated for heat exchange.

What is claimed is:

1. An air conditioning system comprising a refrigerant compressor, a condenser coil connected at one end to the discharge side of said compressor, a suction line accumulator connected to the suction side of said compressor, a heat exchange coil arranged to heat liquid within said 63 accumulator, an expansion valve connected to one end of said heat exchange coil, an evaporator coil connected at one end to said expansion valve and at its other end to said accumulator, means for moving air to be chilled over said evaporator coil, a reheat coil adjacent to and downstream with respect to air ow of said evaporator coil, means when no reheat is required, for routing refrigerant from the other end of said condenser coil into the other end of said heat exchange coil, and when reheat is required, for routing refrigerant from said other end of said condenser coil through said reheat coil into said other end of said heat exchange coil, and means for adjusting said expansion valve to supply refrigerant liquid from said heat exchange coil to said evaporator coil at the rate at which refrigerant is condensed in said condenser coil when no reheat is required, and at the rate at which refrigerant is condensed in said condenser coil and in said reheat coil when reheat is required.

2. An air conditioning system as claimed in claim 1 in which said means for adjusting said expansion valve responds to the temperature and pressure of the refrigerant flowing from said condenser coil into said heat exchange coil when no reheat is required, and responds to the temperature and pressure of the refrigerant owing from said reheat coil into said heat exchange coil when reheat is required. i

3. An air conditioning system comprising a refrigerant compressor, a condenser coil connected at one end to the discharge side of said compressor, a suction line accumulator connected to the suct-ion side of said compressor, a heat exchange coil arranged to heat liquid within said accumulator, an expansion valve connected to one end of said heat exchange coil, an evaporator coil connected at one end to said expansion valve and at its other end to said accumulator, means for moving air to be chilled over said evaporator coil, a reheat coil adjacent to and downstream with respect to air flow of said evaporator coil, a three-way valve connected to the other end of said condenser coil, to the other end of said heat exchange coil, and to one end of said reheat coil, a check-valve connected to the other end of said reheat coil and to said other end of said heat exchange coil, means for adjusting said three-way valve when no reheat is required, to route refrigerant from said other end of said condenser coil to said other end of said heat exchange coil, and when reheat is required, to route refrigerant from said other end of said condenser coil through said reheat coil and said check-valve to said other end of said heat exchange coil, and means for adjusting said expansion valve to supply refrigerant from said heat exchange coil to said evaporator coil at the rate at which refrigerant is condensed in said condenser coil when no reheat is required, and at the rate at which refrigerant is condensed in said condenser coil and in said reheat coil when reheat is required.

4. An air conditioning system as claimed in claim 3 in which said means for adjusting said expansion valve responds to the temperature and the pressure of the refrigerant flowing from said condenser coil into said heat exchange coil when no reheat is required, and responds to the temperature and the pressure of the refrigerant flowing from said reheat coil into said heat exchange coil when reheat is required.

5. A heat pump comprising a refrigerant compressor; an outdoor coil; an indoor air coil; an expansion valve; a suction line accumulator connected to the suction side of said compressor; a heat exchange coil arranged to heat liquid within said accumulator; means for moving air to be conditioned over said indoor coil; a reheat coil adjacent to and downstream with respect to air flow of said indoor coil; control means; means including said control means when indoor air cooling without reheat is required, for routing discharge gas from said compressor to said outdoor fcoil operating as a condenser, for routing referigerant from said outdoor coil through said heat exchange coil and said expansion valve to said indoor coil operating as an evaporator, and for routing gas and unevaporated refrigerant from said indoor coil into said accumulator; means including said control means when indoor air cooling with reheat is required, for routing discharge gas from said compressor to said outdoor coil operating as a condenser, for yrouting refrigerant from said outdoor coil through said reheat coil, through said heat exchange coil and said expansion valve to said indoor coil operating as an evaporator, and for routing gas and unevaporated refrigerant from said indoor coil into said accumulator; means including said control means when indoor air heating is required, for routing discharge gas from said compressor to said indoor coil operating as a condenser, for routing refrigerant from said indoor coil through said reheat coil, through said heat exchange coil and said expansion valve to said outdoor coil operating as an evaporator, and routing gas and unevaporated refrigerant from said outdoor coil into said accumulator; and means for adjusting said expansion valve to supply refrigerant from said heat exchange coil to said indoor coil when indoor air cooling without reheat is required, at the rate at which refrigerant is condensed in said outdoor coil, to supply refrigerant from said heat exchange coil to said indoor coil when indoor air cooling with reheat is required, at the rate at which refrigerant is condensed within said outdoor coil and said reheat coil, and to supply refrigerant from said heat exchange coil when indoor air heating is required, to said outdoor coil at the rate at which refrigerant is condensed in said indoor coil and said reheat coil.

6. A heat pump as claimed in claim in which said means for adjusting said expansion valve responds to the temperature and pressure of the refrigerant flowing from said outdoor coil to said heat exchange coil when indoor air cooling without reheat is required, and responds to the temperature and pressure of the refrigerant fiowing from said reheat coil to said heat exchange coil when indoor air cooling with reheat is required, and when indoor air heating is required.

7. A heat pump comprising a refrigerant compressor; reversal valve means; a discharge tube connecting the discharge side of said compressor to said valve means; a suction line accumulator; a suction gas tube connecting said accumulator to the suction side of said compressor; a heat exchange coil arranged to heat liquid within said accumulator; an expansion valve connected to one end of said heat exchange coil; an outdoor coil; an indoor air coil; means for moving air to be conditioned over said indoor coil; a reheat coil adjacent to and downstream with respect to air iiow of said indoor coil; a three-way valve; first; second; third; fourth and fifth check-valves; a third tube connecting one end of said outdoor coil to said reversal means; a fourth tube containing said first checkvalve connecting the other end of said outdoor coil to said three-way valve; a fifth tube connecting said threeway valve to the other end of said heat exchange coil; a sixth tube connecting said three-way valve to one end of said reheat coil; a seventh tube containing said second check-valve connecting the other end of said reheat coil to said fifth tube; an eighth tube connecting one end of said indoor coil to said reversal means; a ninth tube containing said third and fourth check-valves in series connecting the other end of said indoor coil to said fourth tube; a tenth tube containing said fifth check-valve connecting said one end of said reheat coil to said ninth tube; an eleventh tube connecting said expansion valve between said third and fourth check-valves to said ninth tube; a

twelfth tube connecting said reversal means to said accumulator; said reversal means in air cooling position connecting said discharge tube through said third tube to said outdoor coil operating as a condenser, and connecting said indoor coil operating as an evaporator through said eighth and twelfth tubes to said accumulator, said reversal means in air heating -position connecting said discharge gas tube through said eighth tube to said indoor coil operating as a condenser, and connecting said outdoor coil operating as an evaporator through said third and twelfth tubes to said accumulator; means for adjusting said three-Way valve to a first position when said reversal means is in cooling position and no reheat is required, to route refrigerant from said outdoor coil through said fourth tube, said first check-valve and said fifth tube into said heat exchange coil with refrigerant owing from the latter through said expansion valve, said eleventh and ninth tubes and said third check-valve into said indoor coil; means for adjusting said three-way valve to a second position when said reversal means is in cooling position and reheat is required, to route refrigerant from said outdoor coil through said fourth tube, said first checkvalve, said sixth tube, said reheat coil, said seventh tube, said second check-valve and said fifth tube into said heat exchange coil with refrigerant owing from the latter through said expansion valve, said eleventh and ninth tubes and said third check-valve into said indoor coil; said three-Way valve when air heating is required being in said first position with refrigerant from said indoor coil fiowing through said tenth tube, said fifth check-valve, said reheat lcoil, said seventh tube, said second checkvalve and said fifth tube into said heat exchange coil, with refrigerant flowing from the latter through said expansion valve, said eleventh, ninth and fourth tubes and said fourth check-valve into said outdoor coil; and means for adjusting said expansion valve to supply refrigerant from said heat exchange coil to said indoor coil when indoor air cooling without reheat is required, at the rate at which refrigerant is condensed in said outdoor coil, to supply refrigerant from said heat exchange coil when indoor air cooling with reheat is required, at the rate at which lrefrigerant is condensed in said outdoor and reheat coils, and to supply refrigerant from said heat exchange coil to said outdoor coil, when indoor air heating is required, at the rate at which refrigerant is condensed in said indoor and reheat coils.

8. A heat pump as claimed in claim 7 in which said means for adjusting said expansion valve responds to the temperature and pressure of the refrigerant flowing from said outdoor coil to said heat exchange coil when indoor air cooling without reheat is required, and responds to the temperature and pressure of the refrigerant owing from said reheat coil to said heat exchange coil when indoor air cooling with reheat is required, and when indoor air heating is required.

References Cited by the Examiner UNITED STATES PATENTS 2,195,781 2/1940 Newton 62-173 2,907,178 10/1959 McNatt 62-173 2,952,989 9/1960 Gould 62-173 3,026,687 3/1962 Robson 62-173 3,139,735 7/1964 Malkot 62-173 WILLIAM I. WYE, Primary Examiner, 

1. AN AIR CONDITIONING SYSTEM COMPRISING A REFRIGERANT COMPRESSOR, A CONDENSER COIL CONNECTED AT ONE END TO THE DISCHARGE SIDE OF SAID COMPRESSOR, A SUCTION LINE ACCUMULATOR CONNECTED TO THE SUCTION SIDE OF SAID COMPRESSOR A HEAT EXCHANGE COIL ARRANGED TO HEAT LIQUID WITHIN SAID ACCUMULATOR, AN EXPANSION VALVE CONNECTED TO ONE END OF SAID HEAT EXCHANGE COIL, AN EVAPORATOR COIL CONNECTED AT ONE END TO SAID EXPANSION VALVE AND AT ITS OTHER END TO SAID ACCUMULATOR, MEANS FOR MOVING AIR TO BE CHILLED OVER SAID EVAPORATOR COIL, A REHEAT COIL ADJACENT TO AND DOWNSTREAM WITH RESPECT TO AIR FLOW OF SAID EVAPORATOR COIL, MEANS WHEN NO REHEAT IS REQURIED, FOR ROUTING REFRIGERANT FROM THE OTHER END OF SAID CONDENSER COIL INTO THE OTHER END OF SAID HEAT EXCHANGE COIL, AND WHEN REHEAT IS REQUIRED, FOR ROUTING REFRIGERANT FROM SAID OTHER END OF SAID CONDENSER COIL THROUGH SAID REHEAT COIL INTO SAID OTHER END OF SAID HEAT EXCHANGE COIL, AND MEANS FOR ADJUSTING SAID EXPANSION VALVE TO SUPPLY REFRIGERANT LIQUID FROM SAID HEAT EXCHANGE COIL TO SAID EVAPORATOR COIL AT THE RATE AT WHICH REFRIGERANT IS CONDENSED IN SAID CONDENSER COIL WHEN NO REHEAT IS REQUIRED, AND AT THE RATE AT WHICH REFRIGERANT IS CONDENSED IN AID CONDENSER COIL AND IN SAID REHEAT COIL WHEN REHEAT IS REQUIRED. 